1. Field of the Invention
The invention relates to a medical embolization element which is used in an internal cavity of a tubular organ of a subject, and more specifically, to a medical embolization element which is used for embolizing a bronchus, for example, during treatment of lung emphysema.
2. Description of the Related Art
In general, lung emphysema is a morbid change, which is mainly formed by inhalation of harmful substances due to smoking or the like and mainly features wide destruction in peripheral airways and alveoli. The formation of such morbid change is chronic and progressive, and the respiratory function of a patient whose lung emphysema is in an advanced stage is disordered to a remarkable extent. As the basic elements of disfunction of respiratory disorder due to lung emphysema, there are a reduction in resiliency due to destruction of alveoli and a decrease in the area of a functional alveolar membrane. A plurality of elements of disfunction are combined with these basic elements of disfunction to cause a reduction in ventilation efficiency and a decrease in potential ability of breathing, resulting in respiratory disorder.
The lung tissue of a part affected by lung emphysema suffers overexpansion, and cannot achieve sufficient deflation accompanied by expiration. As the volume occupied by the affected part in a pleural cavity becomes larger, a diaphragm and a chest shift to their inflated positions and the driving force of respiratory movement decreases. The remaining normal lung tissue becomes unable to inflate sufficiently in the pleural cavity, and lowers in ventilation efficiency to a remarkable extent.
Primary methods for treatment of lung emphysema is to give a patient bronchodilators, anti-inflammatory agents and antibiotics for treatment of infectious diseases which may occur as complications, and to apply oxygen inhalation to a patient if the patient's affected part is in an advanced stage. Although there may be some cases where the symptoms of the patient are relieved by such internal medicine treatment, the advance of the patient's morbid state cannot be stopped.
On the other hand, surgical treatment can be given to a lung emphysema patient, such as lung volume reduction surgery and lung transplantation. The lung volume reduction surgery surgically removes a part affected by emphysema to recover the remaining normal pulmonary function. In this manner, it is possible to improve the quality of life of the patient, but it is generally necessary to remove a portion as large as about 30% of the lung of the patient. Since this removal imposes a large burden on the patient, it takes a long time for the patient to recover after the surgical operation.
In the case where lung-emphysema-affected parts and normal lung tissues exist in disorder, it is difficult to separate only morbid tissues, so that there is a case in which even normal lung tissues must be removed. In addition, there is also a case where the shape of a serosa, which contains a pulmonary external surface varies, hinders the inflation of the remaining portion of the lung. As a result, there is a case where the function of the remaining normal lung tissue of the patient cannot be fully retained. In addition, since the line of a removed part differs from a natural state and is exposed to nonuniform pressure, there is a case where the tissue of the removed part is broken and pneumothorax occurs. Since lung emphysema is a progressive disease, the remaining portion of the lung of the patient is affected before long. However, the removal of lung tissue imposes a large burden on the body of the patient and, therefore, is difficult to practice repeatedly.
On the other hand, lung transplantation is the only method that can completely cure lung emphysema by replacing a lung of a patient with a normal lung. However, lung transplantation imposes a very large burden on the body of the patient, and entails problems peculiar to transplantation treatment such as immunological problems and the necessity of securing donors. Neither lung volume reduction surgery nor lung transplantation can be easily practiced, because of the problem of requiring a large surgical operation and hence a huge cost for treatment.
Lung volume reduction surgery and lung transplantation, which are practiced as surgical treatment of lung emphysema, have the following problems:    (1) Since lung volume reduction surgery and lung transplantation need a large surgical operation, a large scar is left on the body of a patient.    (2) Neither lung volume reduction surgery nor lung transplantation can be repeatedly practiced on the same patient.    (3) Lung volume reduction surgery cannot be practiced, if an affected part does not exist at a position where it can be easily removed.    (4) There is a case where lung volume reduction surgery cannot fully ensure the function of the remaining portion of the lung.    (5) Both lung volume reduction surgery and lung transplantation require huge costs.    (6) Pnuemothorax may occur after a surgical operation.    (7) There are large obstacles to be surmounted, such as the necessity of securing donors and a rejection of a transplanted piece.
On the other hand, in PCT WO98/48706, an embolization element which gives treatment to lung emphysema by embolizing a bronchus distributed in a lung-emphysema-affected part is described as a device for solving the above-described problems of surgical treatment of lung emphysema. This embolization element is constructed to prevent new air from flowing into the lung-emphysema-affected part, and the air already stored in the lung-emphysema-affected part is carried by blood or the like and naturally decreases. Consequently, the volume of the lung-emphysema-affected part inflated by air decreases, with the result that it is possible to obtain an advantage similar to lung volume reduction surgery. This embolization element has a construction in which a locking element to be locked by being hooked on a living tissue is provided on a peripheral portion of the body of the embolization element. When the embolization element is to be placed in the body, the locking element provided on the periphery of the body of the embolization element is locked by being hooked on the living tissue, so that the embolization element is placed at a desired position in the body.
The embolization element of PCT WO98/48706 has a construction in which a complicated locking element is provided on the peripheral portion of the body of the embolization element in order to place the embolization element at a desired position in the body. However, PCT WO98/48706 has the problem that since the embolization element for giving treatment to lung emphysema is extremely small in size, the work of providing the complicated locking element on the embolization element is difficult.
The present invention has been made, at least in part, by noting the above-described problems, and an object of the invention is to provide a medical embolization element which is used in an internal cavity of a tubular organ of a subject and does not need a complicated locking element, as well as a method of embolizing a tubular organ.